/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_decimate_fast_q15.c
*
* Description:	Fast Q15 FIR Decimator.
*
* Target Processor: Cortex-M4/Cortex-M3
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup FIR_decimate
 * @{
 */

/**
 * @brief Processing function for the Q15 FIR decimator (fast variant) for Cortex-M3 and Cortex-M4.
 * @param[in] *S points to an instance of the Q15 FIR decimator structure.
 * @param[in] *pSrc points to the block of input data.
 * @param[out] *pDst points to the block of output data
 * @param[in] blockSize number of input samples to process per call.
 * @return none
 *
 * \par Restrictions
 *  If the silicon does not support unaligned memory access enable the macro UNALIGNED_SUPPORT_DISABLE
 *	In this case input, output, state buffers should be aligned by 32-bit
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * This fast version uses a 32-bit accumulator with 2.30 format.
 * The accumulator maintains full precision of the intermediate multiplication results but provides only a single guard bit.
 * Thus, if the accumulator result overflows it wraps around and distorts the result.
 * In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits (log2 is read as log to the base 2).
 * The 2.30 accumulator is then truncated to 2.15 format and saturated to yield the 1.15 result.
 *
 * \par
 * Refer to the function <code>arm_fir_decimate_q15()</code> for a slower implementation of this function which uses 64-bit accumulation to avoid wrap around distortion.
 * Both the slow and the fast versions use the same instance structure.
 * Use the function <code>arm_fir_decimate_init_q15()</code> to initialize the filter structure.
 */

#ifndef UNALIGNED_SUPPORT_DISABLE

void arm_fir_decimate_fast_q15(
    const arm_fir_decimate_instance_q15* S,
    q15_t* pSrc,
    q15_t* pDst,
    uint32_t blockSize)
{
	q15_t* pState = S->pState;                     /* State pointer */
	q15_t* pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
	q15_t* pStateCurnt;                            /* Points to the current sample of the state */
	q15_t* px;                                     /* Temporary pointer for state buffer */
	q15_t* pb;                                     /* Temporary pointer coefficient buffer */
	q31_t x0, x1, c0, c1;                          /* Temporary variables to hold state and coefficient values */
	q31_t sum0;                                    /* Accumulators */
	q31_t acc0, acc1;
	q15_t* px0, *px1;
	uint32_t blkCntN3;
	uint32_t numTaps = S->numTaps;                 /* Number of taps */
	uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M;  /* Loop counters */


	/* S->pState buffer contains previous frame (numTaps - 1) samples */
	/* pStateCurnt points to the location where the new input data should be written */
	pStateCurnt = S->pState + (numTaps - 1u);


	/* Total number of output samples to be computed */
	blkCnt = outBlockSize / 2;
	blkCntN3 = outBlockSize - (2 * blkCnt);


	while(blkCnt > 0u) {
		/* Copy decimation factor number of new input samples into the state buffer */
		i = 2 * S->M;

		do {
			*pStateCurnt++ = *pSrc++;

		} while(--i);

		/* Set accumulator to zero */
		acc0 = 0;
		acc1 = 0;

		/* Initialize state pointer */
		px0 = pState;

		px1 = pState + S->M;


		/* Initialize coeff pointer */
		pb = pCoeffs;

		/* Loop unrolling.  Process 4 taps at a time. */
		tapCnt = numTaps >> 2;

		/* Loop over the number of taps.  Unroll by a factor of 4.
		 ** Repeat until we've computed numTaps-4 coefficients. */
		while(tapCnt > 0u) {
			/* Read the Read b[numTaps-1] and b[numTaps-2]  coefficients */
			c0 = *__SIMD32(pb)++;

			/* Read x[n-numTaps-1] and x[n-numTaps-2]sample */
			x0 = *__SIMD32(px0)++;

			x1 = *__SIMD32(px1)++;

			/* Perform the multiply-accumulate */
			acc0 = __SMLAD(x0, c0, acc0);

			acc1 = __SMLAD(x1, c0, acc1);

			/* Read the b[numTaps-3] and b[numTaps-4] coefficient */
			c0 = *__SIMD32(pb)++;

			/* Read x[n-numTaps-2] and x[n-numTaps-3] sample */
			x0 = *__SIMD32(px0)++;

			x1 = *__SIMD32(px1)++;

			/* Perform the multiply-accumulate */
			acc0 = __SMLAD(x0, c0, acc0);

			acc1 = __SMLAD(x1, c0, acc1);

			/* Decrement the loop counter */
			tapCnt--;
		}

		/* If the filter length is not a multiple of 4, compute the remaining filter taps */
		tapCnt = numTaps % 0x4u;

		while(tapCnt > 0u) {
			/* Read coefficients */
			c0 = *pb++;

			/* Fetch 1 state variable */
			x0 = *px0++;

			x1 = *px1++;

			/* Perform the multiply-accumulate */
			acc0 = __SMLAD(x0, c0, acc0);
			acc1 = __SMLAD(x1, c0, acc1);

			/* Decrement the loop counter */
			tapCnt--;
		}

		/* Advance the state pointer by the decimation factor
		 * to process the next group of decimation factor number samples */
		pState = pState + S->M * 2;

		/* Store filter output, smlad returns the values in 2.14 format */
		/* so downsacle by 15 to get output in 1.15 */
		*pDst++ = (q15_t)(__SSAT((acc0 >> 15), 16));
		*pDst++ = (q15_t)(__SSAT((acc1 >> 15), 16));

		/* Decrement the loop counter */
		blkCnt--;
	}



	while(blkCntN3 > 0u) {
		/* Copy decimation factor number of new input samples into the state buffer */
		i = S->M;

		do {
			*pStateCurnt++ = *pSrc++;

		} while(--i);

		/*Set sum to zero */
		sum0 = 0;

		/* Initialize state pointer */
		px = pState;

		/* Initialize coeff pointer */
		pb = pCoeffs;

		/* Loop unrolling.  Process 4 taps at a time. */
		tapCnt = numTaps >> 2;

		/* Loop over the number of taps.  Unroll by a factor of 4.
		 ** Repeat until we've computed numTaps-4 coefficients. */
		while(tapCnt > 0u) {
			/* Read the Read b[numTaps-1] and b[numTaps-2]  coefficients */
			c0 = *__SIMD32(pb)++;

			/* Read x[n-numTaps-1] and x[n-numTaps-2]sample */
			x0 = *__SIMD32(px)++;

			/* Read the b[numTaps-3] and b[numTaps-4] coefficient */
			c1 = *__SIMD32(pb)++;

			/* Perform the multiply-accumulate */
			sum0 = __SMLAD(x0, c0, sum0);

			/* Read x[n-numTaps-2] and x[n-numTaps-3] sample */
			x0 = *__SIMD32(px)++;

			/* Perform the multiply-accumulate */
			sum0 = __SMLAD(x0, c1, sum0);

			/* Decrement the loop counter */
			tapCnt--;
		}

		/* If the filter length is not a multiple of 4, compute the remaining filter taps */
		tapCnt = numTaps % 0x4u;

		while(tapCnt > 0u) {
			/* Read coefficients */
			c0 = *pb++;

			/* Fetch 1 state variable */
			x0 = *px++;

			/* Perform the multiply-accumulate */
			sum0 = __SMLAD(x0, c0, sum0);

			/* Decrement the loop counter */
			tapCnt--;
		}

		/* Advance the state pointer by the decimation factor
		 * to process the next group of decimation factor number samples */
		pState = pState + S->M;

		/* Store filter output, smlad returns the values in 2.14 format */
		/* so downsacle by 15 to get output in 1.15 */
		*pDst++ = (q15_t)(__SSAT((sum0 >> 15), 16));

		/* Decrement the loop counter */
		blkCntN3--;
	}

	/* Processing is complete.
	 ** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
	 ** This prepares the state buffer for the next function call. */

	/* Points to the start of the state buffer */
	pStateCurnt = S->pState;

	i = (numTaps - 1u) >> 2u;

	/* copy data */
	while(i > 0u) {
		*__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
		*__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;

		/* Decrement the loop counter */
		i--;
	}

	i = (numTaps - 1u) % 0x04u;

	/* copy data */
	while(i > 0u) {
		*pStateCurnt++ = *pState++;

		/* Decrement the loop counter */
		i--;
	}
}

#else


void arm_fir_decimate_fast_q15(
    const arm_fir_decimate_instance_q15* S,
    q15_t* pSrc,
    q15_t* pDst,
    uint32_t blockSize)
{
	q15_t* pState = S->pState;                     /* State pointer */
	q15_t* pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
	q15_t* pStateCurnt;                            /* Points to the current sample of the state */
	q15_t* px;                                     /* Temporary pointer for state buffer */
	q15_t* pb;                                     /* Temporary pointer coefficient buffer */
	q15_t x0, x1, c0;                              /* Temporary variables to hold state and coefficient values */
	q31_t sum0;                                    /* Accumulators */
	q31_t acc0, acc1;
	q15_t* px0, *px1;
	uint32_t blkCntN3;
	uint32_t numTaps = S->numTaps;                 /* Number of taps */
	uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M;  /* Loop counters */


	/* S->pState buffer contains previous frame (numTaps - 1) samples */
	/* pStateCurnt points to the location where the new input data should be written */
	pStateCurnt = S->pState + (numTaps - 1u);


	/* Total number of output samples to be computed */
	blkCnt = outBlockSize / 2;
	blkCntN3 = outBlockSize - (2 * blkCnt);

	while(blkCnt > 0u) {
		/* Copy decimation factor number of new input samples into the state buffer */
		i = 2 * S->M;

		do {
			*pStateCurnt++ = *pSrc++;

		} while(--i);

		/* Set accumulator to zero */
		acc0 = 0;
		acc1 = 0;

		/* Initialize state pointer */
		px0 = pState;

		px1 = pState + S->M;


		/* Initialize coeff pointer */
		pb = pCoeffs;

		/* Loop unrolling.  Process 4 taps at a time. */
		tapCnt = numTaps >> 2;

		/* Loop over the number of taps.  Unroll by a factor of 4.
		 ** Repeat until we've computed numTaps-4 coefficients. */
		while(tapCnt > 0u) {
			/* Read the Read b[numTaps-1] coefficients */
			c0 = *pb++;

			/* Read x[n-numTaps-1] for sample 0 and for sample 1 */
			x0 = *px0++;
			x1 = *px1++;

			/* Perform the multiply-accumulate */
			acc0 += x0 * c0;
			acc1 += x1 * c0;

			/* Read the b[numTaps-2] coefficient */
			c0 = *pb++;

			/* Read x[n-numTaps-2] for sample 0 and sample 1 */
			x0 = *px0++;
			x1 = *px1++;

			/* Perform the multiply-accumulate */
			acc0 += x0 * c0;
			acc1 += x1 * c0;

			/* Read the b[numTaps-3]  coefficients */
			c0 = *pb++;

			/* Read x[n-numTaps-3] for sample 0 and sample 1 */
			x0 = *px0++;
			x1 = *px1++;

			/* Perform the multiply-accumulate */
			acc0 += x0 * c0;
			acc1 += x1 * c0;

			/* Read the b[numTaps-4] coefficient */
			c0 = *pb++;

			/* Read x[n-numTaps-4] for sample 0 and sample 1 */
			x0 = *px0++;
			x1 = *px1++;

			/* Perform the multiply-accumulate */
			acc0 += x0 * c0;
			acc1 += x1 * c0;

			/* Decrement the loop counter */
			tapCnt--;
		}

		/* If the filter length is not a multiple of 4, compute the remaining filter taps */
		tapCnt = numTaps % 0x4u;

		while(tapCnt > 0u) {
			/* Read coefficients */
			c0 = *pb++;

			/* Fetch 1 state variable */
			x0 = *px0++;
			x1 = *px1++;

			/* Perform the multiply-accumulate */
			acc0 += x0 * c0;
			acc1 += x1 * c0;

			/* Decrement the loop counter */
			tapCnt--;
		}

		/* Advance the state pointer by the decimation factor
		 * to process the next group of decimation factor number samples */
		pState = pState + S->M * 2;

		/* Store filter output, smlad returns the values in 2.14 format */
		/* so downsacle by 15 to get output in 1.15 */

		*pDst++ = (q15_t)(__SSAT((acc0 >> 15), 16));
		*pDst++ = (q15_t)(__SSAT((acc1 >> 15), 16));


		/* Decrement the loop counter */
		blkCnt--;
	}

	while(blkCntN3 > 0u) {
		/* Copy decimation factor number of new input samples into the state buffer */
		i = S->M;

		do {
			*pStateCurnt++ = *pSrc++;

		} while(--i);

		/*Set sum to zero */
		sum0 = 0;

		/* Initialize state pointer */
		px = pState;

		/* Initialize coeff pointer */
		pb = pCoeffs;

		/* Loop unrolling.  Process 4 taps at a time. */
		tapCnt = numTaps >> 2;

		/* Loop over the number of taps.  Unroll by a factor of 4.
		 ** Repeat until we've computed numTaps-4 coefficients. */
		while(tapCnt > 0u) {
			/* Read the Read b[numTaps-1] coefficients */
			c0 = *pb++;

			/* Read x[n-numTaps-1] and sample */
			x0 = *px++;

			/* Perform the multiply-accumulate */
			sum0 += x0 * c0;

			/* Read the b[numTaps-2] coefficient */
			c0 = *pb++;

			/* Read x[n-numTaps-2] and  sample */
			x0 = *px++;

			/* Perform the multiply-accumulate */
			sum0 += x0 * c0;

			/* Read the b[numTaps-3]  coefficients */
			c0 = *pb++;

			/* Read x[n-numTaps-3] sample */
			x0 = *px++;

			/* Perform the multiply-accumulate */
			sum0 += x0 * c0;

			/* Read the b[numTaps-4] coefficient */
			c0 = *pb++;

			/* Read x[n-numTaps-4] sample */
			x0 = *px++;

			/* Perform the multiply-accumulate */
			sum0 += x0 * c0;

			/* Decrement the loop counter */
			tapCnt--;
		}

		/* If the filter length is not a multiple of 4, compute the remaining filter taps */
		tapCnt = numTaps % 0x4u;

		while(tapCnt > 0u) {
			/* Read coefficients */
			c0 = *pb++;

			/* Fetch 1 state variable */
			x0 = *px++;

			/* Perform the multiply-accumulate */
			sum0 += x0 * c0;

			/* Decrement the loop counter */
			tapCnt--;
		}

		/* Advance the state pointer by the decimation factor
		 * to process the next group of decimation factor number samples */
		pState = pState + S->M;

		/* Store filter output, smlad returns the values in 2.14 format */
		/* so downsacle by 15 to get output in 1.15 */
		*pDst++ = (q15_t)(__SSAT((sum0 >> 15), 16));

		/* Decrement the loop counter */
		blkCntN3--;
	}

	/* Processing is complete.
	 ** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
	 ** This prepares the state buffer for the next function call. */

	/* Points to the start of the state buffer */
	pStateCurnt = S->pState;

	i = (numTaps - 1u) >> 2u;

	/* copy data */
	while(i > 0u) {
		*pStateCurnt++ = *pState++;
		*pStateCurnt++ = *pState++;
		*pStateCurnt++ = *pState++;
		*pStateCurnt++ = *pState++;

		/* Decrement the loop counter */
		i--;
	}

	i = (numTaps - 1u) % 0x04u;

	/* copy data */
	while(i > 0u) {
		*pStateCurnt++ = *pState++;

		/* Decrement the loop counter */
		i--;
	}
}


#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

/**
 * @} end of FIR_decimate group
 */
